Looking for Wiring Advice

I'm looking for some help/advice with a wiring question from someone who has access to the wiring diagram for a 14 Access Cab. I upgraded my stereo, adding a backup camera which I mounted in the bumper adjacent to the license plate. What I failed to consider was that at night with the lights on, the license plate lights blind the camera. So what I'd like to do is install a relay that would interrupt power to the license plate lights whenever the back-up lights came on. The wiring would look something like this:

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Can someone tell me what lines I need to tap into to accomplish this?